It can be seen from the research that the appearance of the motor housing is completely expressed by the EPS foam pattern. The quality of the casting blank depends on the quality of the foam pattern. Every production of a blank requires a foam model. It is easy to understand that the design and manufacturing quality of EPC dies is directly related to the quality of the final castings. In this paper, the design method of sand core casting mold is discussed, and the material and working mode of EPC mold are very different from that of sand core mold. In the process of mold design and manufacturing of EPC, we should pay attention to the following points:
(1) Selection of mold parting surface
One of the advantages of EPC process compared with sand core process is that there is no need to lower the mold core, especially in the face of complex castings. Whether the mold design is reasonable or not, the choice of parting surface is very important. Complex models are generally difficult to produce completely through a cavity, and the foam mold can be bonded to each other. Therefore, by decomposing the foam model, the complex model can be partitioned into a simple model to facilitate the production of foam models. In addition, it is also convenient for positioning and bonding.
(2) Mold eyelet
The pre foaming to a certain rate of plastic beads is blown into the mold cavity through the feed hole. Under certain vapor pressure, the bead in the mold cavity expands and becomes a foam model, which is the forming principle of the foam model. When the foam is inside the mold cavity, it needs the gas chamber with uniform inlet high temperature steam, and the height of the gas chamber is not less than 30mm, so that the high temperature steam can be buffered in the gas chamber and can reach the cavity evenly through the air hole. The air hole shall be evenly arranged in the mold cavity with a spacing of 20-30mm. If the air hole cannot be placed due to limited conditions, a small diameter drill can be used to drill a small hole in the corresponding position for ventilation, with a hole diameter of about 1mm.
(3) Die wall thickness
In, there are not too many requirements for mold wall thickness, but in , when the mold works, it needs rapid temperature rise and rapid cooling, so the mold must be designed as much as possible with the same mold wall thickness as the inner cavity, that is, the wall thickness of the mold section is basically the same, generally 8-16mm. If the mold wall thickness changes too much, it needs to be heated or cooled The beads in the cavity will have local overburning or local raw meal.
(4) Feed hole and bar
The feed hole shall be designed on the side close to the worker for convenient operation and bead filling. The distance between the feed hole and the mold cavity shall be the same for uniform filling density. The material of the retaining bar shall be consistent with that of the die body, so as to avoid the formation of raw meal at the feed port due to the uneven heating of different materials.
(5) Core pulling mechanism and movable block
The advantages of EPC mold in the complex model make EPC mold often encounter complex models when designing mold. The characteristics of these models are that it is difficult to open the mold in a single direction at one time, only the structure with the same direction of mold opening can be formed by the combination of upper and lower mold, and the part with different direction of mold opening needs to adopt the ingenious structure or movable block for modeling. When designing the core pulling mechanism, it is necessary to ensure the clearance of the junction of each structure. If it is too large, it will leak, the steam pressure will drop, and the foam particles will not be steamed easily.